Keeping Unvented Tiny House 25 degree gable roof dry/mold free. How to?
I’m over in Eastern Washington getting close to completion on my 18’ mini house. As me and my contractors were putting on our OSB roof deck I still hadn’t decided whether to go with a single layer or 2 layers with 1 inch of R10 foamular between. The extra weight, $1,200 cost, extra 3 inches of height over 13’ 6in, and the cosmetic fact we would have had to add another piece of LP smart trim vs the current 7.25 belly band that was flush with the single layer OSB, I decided to stick with the single layer:
*Now we’ll be putting Titanium PSU 30 ice and water shield over the OSB and then standing seam metal.
*Inside is 2×6 framing and I’m thinking Sika Rmax foam polyiso friction fit with a little sika insulation sealant at the seams. With 5.5in this would be R33. 2’’ pieces, more 2’’ pieces, and then 1.5’’ pieces. Then taped drywall to block out inside air. Then some sort of wood t & g.
The Sika Rmax has a foil side and a guy at the local building supply store told me to leave a gap between the foil and the drywall to reflect? Yes? No? If so then maybe I’d do 5in total of Rmax polyiso.
Also, a few people have recommended a small 2in aluminum vent/Louver set in every 2×6 cavity of the interior ceiling. Good idea? That seems to be counterproductive to the idea of not letting interior air up into the ceiling cavity. If air and water got through the I & W, how would it get through the Rmax and sika sealant at seams to even reach the little vents set in the drywall/t & g? I have no idea what to do and just want the best possible outcome with the standing seam metal, ice and water shield, OSB, unvented, etc.
Take care and thank you for feedback.
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